The use and construction of fluidic check valves for rendering unidirectional the otherwise reversing flows of liquid or gas streams is well known in the art of practical fluid mechanics. Such valves are in use today in a wide variety of fluid systems and environments, being embodied in a number of mechanical configurations linked by a single functional chore, the prohibition of fluid flow in an undesired, reverse direction.
One particular application in which commercially available check valves have proved to be unsuitable is in the hydraulic shaft damping system of a high speed gas turbine engine or the like. In such a system, a continuous flow of oil or other damping fluid is introduced into an annular space formed between an outer stationary support cylinder and an inner cylinder or shaft bearing race support which is subject to a transverse orbital movement as a result of some imbalance in the rotating portion of the gas turbine.
The transverse orbital motion of the inner cylinder results in a rotating pressure wave circumnavigating the inner cylinder at a speed equivalent to that of the transverse cylinder oscillation. For those bearing damping systems wherein the flow of damping fluid is introduced at one or more points disposed about the circumference of the annulus, it has been found that the orbiting pressure wave will drive the hydraulic fluid back down the fluid supply line, resulting in interrupted or unsteady flow and possible local cavitation within the annulus.
Attempts to restrict this periodic reverse flow in the supply line by installing commercially available check valves have proved unsatisfactory due to the inability of such prior art valves to perform adequately under the high frequency flow reversals experienced. Experimentation has verified the unsuitability for these prior art valves at oscillation rates of 80 Hz or above, while desired turbine engine operating speeds result in the occurrence of flow reversals at frequencies of 130 Hz or higher. The inability of the commercial industry to supply check valves responsive to the high frequency environment discussed hereinabove has resulted in undesirable limitations being imposed gas turbine start-up times and power levels in order to avoid inadequately damped, and hence possibly damaging, operation.